The invention relates to a control system for an internal combustion engine with at least one electromechanically activated charge cycle valve, an injection system and an ignition system, which are each operated by output stages.
Internal combustion engines whose charge cycle valves are electromechanically activated are known. In contrast to camshaft-activated valves, these valves are actuated, so as to open and close as a function of the rotational position of the crankshaft; there is no fixed mechanical coupling to the crankshaft. Electromechanical final controlling elements for charge cycle valves are known, for example, from German Utility Model DE 297 19 502 U1 (which corresponds to Eppich et al., U.S. Pat. No. 5,980,235) or European Patent Application EP 0 724 067 A1 (which corresponds to Sono et al., U.S. Pat. No. 5,752,478). They have a rest position that is located between a closed position and an open position, from which they can be deflected by electromagnets.
The respective winding is energized in order to open or close a valve. The necessary current is greater in the capture phase than in the holding phase, in which the valve is held in an end position.
Whereas the control times are not predefined in the operational control unit of the internal combustion engine in the case of a conventional, camshaft-activated valve drive, it is necessary to calculate and predefine appropriate control times in the case of electromechanically activated valves.
The injection system and ignition system of an internal combustion engine are usually each actuated by output stages that are disposed in the operational control unit of the internal combustion engine.
The operational control unit and the valve control unit communicate with one another, usually via a data bus, for example a CAN data bus.
In contrast to camshaft-activated valves, electromechanically activated valves can be opened and closed independently of the operation of the internal combustion engine. When the electromechanical activation of the valve fails, it is therefore possible for the respective valve to remain opened when it is not desirable. A valve may fail, for example, due to a failure of the actuating unit, of the output stage that actuates the actuating unit, or due to a fault in the valve control unit, which also occurs only for a brief time under certain circumstances.
Such a failure is detected by the valve control unit. However, the valve control unit cannot signal this in good time to the operational control unit via the CAN bus because generally data is only exchanged via this bus connection every 180xc2x0 crankshaft angle.
If such a failure occurs at an inlet valve, ignition into the intake tract or the intake manifold may therefore occur, which can lead to damage to the intake tract, in particular if the latter is fabricated from plastic.
Furuta (U.S. Pat. No. 5,890,078) discloses a control system for an internal combustion engine in which, in addition to an operational control unit that has a processor, a control unit is provided that has a processor and exchanges data with the operational control unit via a bidirectional communications line. The additional control unit controls the activating elements for the ignition, injection, adjustment of throttle valve, and the shifting of an automatic transmission. If the additional control unit determines that a fault has occurred either in the operational control units or at the interface between the two control units, the additional control unit assumes the function of calculating the control variables in order to be able to control the activating elements independently of the operational control unit. This document is not concerned with the control of an internal combustion engine with electromechanically activated charge cycle valves.
European Patent Application EP 0 309 968 A1, which corresponds to Kashimura et al. U.S. Pat. No. 4,893,590, discloses an electronic control unit for use in a motor vehicle. The electronic control unit is disposed in the vicinity of the internal combustion engine and is thermally connected to the cooling circuit of the internal combustion engine in order to avoid overheating.
It is accordingly an object of the invention to provide a control system for an internal combustion engine with electromechanically activated charge cycle valves that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that has at least one electromechanically activated charge cycle valve that prevents undesired ignition of a fuel/air mixture even when the electromagnetic actuating charge cycle valve fails.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a control system for an internal combustion engine having an electromechanically activated charge cycle valve, an injection system, and an ignition system, each with respective output stages. The control system includes a bi-directional communications line, an operational control unit, and a valve control unit. The operational control unit for the internal combustion engine connects to the bi-directional communications line and has a processor determining pre-specified values for activating the injection system and the charge cycle valve. The valve control unit has a processor exchanging data with the operational control unit via the bi-directional communications line. The valve control unit contains the output stages for the ignition system as well as for the electromechanically activated charge cycle valve. The valve control unit actuates the output stages for the electromechanically activated charge cycle valve as a function of the data received from the operational control unit for detecting a failure of an electromechanically activated charge cycle valve leading to the charge cycle valve not being closed in the cylinder of the internal combustion engine and interrupting the ignition in the affected cylinder by suitably actuating the output stage of the ignition system in order to prevent ignition of the fuel/air mixture in the affected cylinder.
In order to be able to prevent the ignition of a fuel/air mixture when an electromechanically activated charge cycle valve fails, the output stage of the ignition system is integrated into the valve control unit. As a result, when a valve failure is detected, the valve control unit can promptly prevent the ignition because time-consuming communication via a bus to the operational control unit of the internal combustion engine is no longer necessary.
The ignition can be shut off for all the cylinders, but is also possible on a cylinder-specific basis.
All the output stages for the injection system, valve activation and ignition system are advantageously disposed in the valve control unit so that the operational control unit is free of output stages relating to the latter. As a result, the thermal connection or accommodation on the internal combustion engine is significantly simplified. Furthermore, the combination of all the output stages in the valve control unit provides the advantage that the water cooling which is desirable in any case for the output stages of the electromechanical valve activation and which can be brought about by the connection to the coolant circuit of the internal combustion engine improves the thermal conditions in the other output stages.
The operational control unit now only requests a desired torque or a desired load of the internal combustion engine from the valve control unit in which all the output stages are combined. Hence, the valve control unit is then a torque control unit that selects the ignition time, injection time, emission feedback rate, and valve opening times independently and sets them correspondingly at the output stages.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a control system for an internal combustion engine with electromechanically activated charge cycle valves, it is nevertheless not intended to be limited to the details shown, because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.